134 research outputs found
User Activity Detection and Channel Estimation for Grant-Free Random Access in LEO Satellite-Enabled Internet-of-Things
With recent advances on the dense low-earth orbit (LEO) constellation, LEO
satellite network has become one promising solution to providing global
coverage for Internet-of-Things (IoT) services. Confronted with the sporadic
transmission from randomly activated IoT devices, we consider the random access
(RA) mechanism, and propose a grant-free RA (GF-RA) scheme to reduce the access
delay to the mobile LEO satellites. A Bernoulli-Rician message passing with
expectation maximization (BR-MP-EM) algorithm is proposed for this
terrestrial-satellite GF-RA system to address the user activity detection (UAD)
and channel estimation (CE) problem. This BR-MP-EM algorithm is divided into
two stages. In the inner iterations, the Bernoulli messages and Rician messages
are updated for the joint UAD and CE problem. Based on the output of the inner
iterations, the expectation maximization (EM) method is employed in the outer
iterations to update the hyper-parameters related to the channel impairments.
Finally, simulation results show the UAD and CE accuracy of the proposed
BR-MP-EM algorithm, as well as the robustness against the channel impairments.Comment: 14 pages, 9 figures, accepted by Internet of Things Journa
Detection of a superconducting phase in a two-atom layer of hexagonal Ga film grown on semiconducting GaN(0001)
The recent observation of superconducting state at atomic scale has motivated
the pursuit of exotic condensed phases in two-dimensional (2D) systems. Here we
report on a superconducting phase in two-monolayer crystalline Ga films
epitaxially grown on wide band-gap semiconductor GaN(0001). This phase exhibits
a hexagonal structure and only 0.552 nm in thickness, nevertheless, brings
about a superconducting transition temperature Tc as high as 5.4 K, confirmed
by in situ scanning tunneling spectroscopy, and ex situ electrical
magneto-transport and magnetization measurements. The anisotropy of critical
magnetic field and Berezinski-Kosterlitz-Thouless-like transition are observed,
typical for the 2D superconductivity. Our results demonstrate a novel platform
for exploring atomic-scale 2D superconductor, with great potential for
understanding of the interface superconductivity
Expression profiles of five FT-like genes and functional analysis of PhFT-1 in a Phalaenopsis hybrid
Background: Phalaenopsis is an important ornamental flowering plant
that belongs to the Orchidaceae family and is cultivated worldwide.
Phalaenopsis has a long juvenile phase; therefore, it is important to
understand the genetic elements regulating the transition from
vegetative phase to reproductive phase. In this study, FLOWERING LOCUS
T (FT) homologs in Phalaenopsis were cloned, and their effects on
flowering were analyzed. Results: A total of five FT-like genes were
identified in Phalaenopsis. Phylogenetic and expression analyses of
these five FT-like genes indicated that some of these genes might
participate in the regulation of flowering. A novel FT-like gene,
PhFT-1, distantly related to previously reported FT genes in
Arabidopsis and other dicot crops, was also found to be a positive
regulator of flowering as heterologous expression of PhFT-1 in
Arabidopsis causes an early flowering phenotype. Conclusions: Five FT
homologous genes from Phalaenopsis orchid were identified, and PhFT-1
positively regulates flowering
Interfacial āSingleāAtomāināDefectsā Catalysts Accelerating Li + Desolvation Kinetics for LongāLifespan LithiumāMetal Batteries
The lithium-metal anode is a promising candidate for realizing high-energy-density batteries owing to its high capacity and low potential. However, several rate-limiting kinetic obstacles, such as the desolvation of Li+ solvation structure to liberate Li, Li nucleation, and atom diffusion, cause heterogeneous spatial Li-ion distribution and fractal plating morphology with dendrite formation, leading to low Coulombic efficiency and depressive electrochemical stability. Herein, differing from pore sieving effect or electrolyte engineering, atomic iron anchors to cation vacancy-rich Co embedded in 3D porous carbon (SAFe/CVRCS@3DPC) is proposed and demonstrated as catalytic kinetic promoters. Numerous free Li ions are electrocatalytically dissociated from the Li solvation complex structure for uniform lateral diffusion by reducing desolvation and diffusion barriers via SAFe/CVRCS@3DPC, realizing smooth dendrite-free Li morphologies, as comprehensively understood by combined in situ/ex situ characterizations. Encouraged by SAFe/CVRCS@3DPC catalytic promotor, the modified Li-metal anodes achieve smooth plating with a long lifespan (1600 h) and high Coulombic efficiency without any dendrite formation. Paired with the LiFePO cathode, the full cell (10.7 mg cm) stabilizes a capacity retention of 90.3% after 300 cycles at 0.5 C, signifying the feasibility of using interfacial catalysts for modulating Li behaviors toward practical applications
Accelerated Liāŗ Desolvation for Diffusion Booster Enabling LowāTemperature Sulfur Redox Kinetics via Electrocatalytic CarbonāGrazftedāCoP Porous Nanosheets
Lithiumāsulfur (LiāS) batteries are famous for their high energy density and low cost, but prevented by sluggish redox kinetics of sulfur species due to depressive Li ion diffusion kinetics, especially under low-temperature environment. Herein, a combined strategy of electrocatalysis and pore sieving effect is put forward to dissociate the Li+ solvation structure to stimulate the free Li+ diffusion, further improving sulfur redox reaction kinetics. As a protocol, an electrocatalytic porous diffusion-boosted nitrogen-doped carbon-grafted-CoP nanosheet is designed via forming the NCoP active structure to release more free Li+ to react with sulfur species, as fully investigated by electrochemical tests, theoretical simulations and in situ/ex situ characterizations. As a result, the cells with diffusion booster achieve desirable lifespan of 800 cycles at 2 C and excellent rate capability (775 mAh gā1 at 3 C). Impressively, in a condition of high mass loading or low-temperature environment, the cell with 5.7 mg cmā2 stabilizes an areal capacity of 3.2 mAh cmā2 and the charming capacity of 647 mAh gā1 is obtained under 0 Ā°C after 80 cycles, demonstrating a promising route of providing more free Li ions toward practical high-energy LiāS batteries
Single-pixel computational ghost imaging with helicity-dependent metasurface hologram
A helicity-dependent computational ghost image generated by a metasurface hologram offers a promising optical encryption scheme.</jats:p
Integrative proteomic and metabonomic profiling elucidates amino acid and lipid metabolism disorder in CA-MRSA-infected breast abscesses
ObjectiveBacterial culture and drug sensitivity testing have been the gold standard for confirming community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) infection in breast abscess with a long history. However, these tests may delay treatment and increase the risk of nosocomial infections. To handle and improve this critical situation, this study aimed to explore biomarkers that could facilitate the rapid diagnosis of CA-MRSA infection.MethodsThis study for the first time applied label-free quantitative proteomics and non-targeted metabonomics to identify potential differentially expressed proteins (DEPs) and differentially expressed metabolites (DEMs) in breast abscess infected with CA-MRSA compared to methicillin-susceptible S. aureus (MSSA). The two omics data were integrated and analyzed using bioinformatics, and the results were validated using Parallel Reaction Monitoring (PRM). Receiver operating characteristic (ROC) curves were generated to evaluate the predictive efficiency of the identified biomarkers for diagnosing CA-MRSA infection.ResultsAfter using the above-mentioned strategies, 109 DEPs were identified, out of which 86 were upregulated and 23 were downregulated. Additionally, a total of 61 and 26 DEMs were initially screened in the positive and negative ion modes, respectively. A conjoint analysis indicated that the amino acid metabolism, glycosphingolipid biosynthesis, and glycerophospholipid metabolism pathways were co-enriched by the upstream DEPs and downstream DEMs, which may be involved in structuring the related network of CA-MRSA infection. Furthermore, three significant DEMs, namely, indole-3-acetic acid, L-(ā)-methionine, and D-sedoheptulose 7-phosphate, displayed good discriminative abilities in early identification of CA-MRSA infection in ROC analysis.ConclusionAs there is limited high-quality evidence and multiple omics research in this field, the explored candidate biomarkers and pathways may provide new insights into the early diagnosis and drug resistance mechanisms of CA-MRSA infection in Chinese women
Isothiocyanates induce oxidative stress and suppress the metastasis potential of human non-small cell lung cancer cells
<p>Abstract</p> <p>Background</p> <p>Isothiocyanates are natural compounds found in consumable cruciferous vegetables. They have been shown to inhibit chemical carcinogenesis by a wide variety of chemical carcinogens in animal models. Recent studies have also shown that isothiocyanates have antitumor activity, inhibiting the growth of several types of cultured human cancer cells. Our previous study showed that PEITC inhibited human leukemia cells growth by inducing apoptosis. However, the effect of isothiocyanates on lung cancer cell metastasis has not been studied. In the present study, we investigated the inhibitory effects of BITC and PEITC on metastatic potential of highly metastatic human lung cancer L9981 cells.</p> <p>Methods</p> <p>Cell migration and invasion were measured by wound healing assay and transwell chemotaxis assay. Expression of metastasis-related genes was assessed by quantitative RT-PCR and Western blotting. The mechanisms of action were evaluated by flow cytometry, reporter assay and Western blotting.</p> <p>Results</p> <p>Our data showed that both BITC and PEITC inhibited L9981 cell growth in a dose-dependent manner, the IC50 values were 5.0 and 9.7 Ī¼M, respectively. Cell migrations were reduced to 8.1% and 16.5% of control, respectively; and cell invasions were reduced to 2.7% and 7.3% of control, respectively. Metastasis-related genes MMP-2, Twist and Ī²-catenin were also modulated. BITC and PEITC inhibited cell survival signaling molecules Akt and NFĪŗB activation. Moreover, BITC and PEITC increased ROS generation and caused GSH depletion. Pretreatment with NAC blocked BITC and PEITC induced ROS elevation and NFĪŗB inhibition.</p> <p>Conclusion</p> <p>Our results indicated that BITC and PEITC suppress lung cancer cell metastasis potential by modulation of metastasis-related gene expression, inhibition of Akt/NFĪŗB pathway. Induction of oxidative stress may play an important role.</p
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